A portable blood glucose level measuring device has been put to practical use for checking the blood glucose level by an individual who stays at home or away from home. To measure the blood glucose level using such a measuring device, a biosensor may be set to the measuring device for providing an enzyme reaction field, to which blood is supplied. In doing this, a lancing apparatus having a skin-lancing needle may be used for facilitating the bleeding from the skin. From a sanitary point of view, the skin-lancing needle is provided as a disposable lancet. An example of lancet is disclosed in the gazette of JP-U-5-88503. The lancet disclosed in the gazette, suitable for reducing the manufacturing cost due to the reduced number of parts, has a structure shown in FIGS. 27A and 28A of the present application.
The lancet 8 of FIG. 27A includes a needle hub 82 supported by a housing 80 via a breakable portion 81. The needle hub 82 holds a lancing needle 83. The housing 80 is formed with a first opening 80a for allowing access to the rear end 82a of the needle hub 82 to push it, and with a second opening 80b for allowing the projection of the lancing needle 81. At the second opening 80b, a cap 84 is provided for closure. The cap 84 includes a breakable portion 84a so that the front portion 84b of the cap 84 can be removed, as shown in FIG. 27B. The front portion 84b of the cap 84 includes a needle tip accommodation space 84c. 
In using the lancet 8, the front portion 84b of the cap 84 is removed, and then the rear end 82a of the needle hub 82 is fitted to a pushing member 85 of the lancing apparatus not shown in the figure. By operating the pushing member 85, the breakable portion 81 is broken, thereby permitting the needle hub 82 to move in the pushing direction (the direction indicated by the arrow A in FIG. 27). As a result, the tip of the lancing needle 83 projects forward from the second opening 80b, so that the lancing needle 83 can lance the skin. After the lancing is finished, the front portion 84b of the cap 84 is turned over, as shown in FIG. 27C, to be attached to the rear portion of the cap 84. Thus, the needle tip is accommodated in the accommodation space 84c. 
The lancet 9 shown in FIG. 28A includes a housing 92 in which a needle hub 90 is held via a resilient portion 91. The housing 92 has an opening 92b to which a cap 94 is attached. The cap 94 includes a breakable portion 94a and an accommodation space 94c. 
In the lancet 9 again, after the front end 94b of the cap 94 is removed, the front end of a lancing needle 93 is caused to project from the housing 92, as the rear end 90a of the needle hub 90 is pushed in the direction of the illustrated arrow A in FIG. 28B. Then, when the pushing force is removed, the restoring force of the resilient member 91 brings the needle hub 90 back to the initial position, so that the lancing needle 93 is accommodated in the housing 92.
In the lancets 8, 9 shown in FIGS. 27 and 28, the lancing needles 83, 93 are left projecting from the needle hubs 82, 90. Specifically, the lancing needles 83, 93 are embedded in the needle hubs 82, 90 by insert molding except for the front ends. However, in insert molding the lancing needles 83, 93 with the needle tips 83, 93 exposed, care should be taken so as not to bend the needle tips, which makes the manufacture difficult. Further, the needle hubs 82, 90 are formed integral with the housings 80, 90 via the breakable portion 81 or the resilient portion 91, and the molding for such an integral configuration is difficult. Moreover, in attaching the caps 84, 94 to the housing 80, 92 via the breakable portion 81 or the resilient portion 91, care should be taken so as not to bend the needle tips, which causes the operation efficiency to deteriorate. In summary, the lancets 8, 9 shown in FIGS. 27 and 28 are disadvantageous in terms of production cost because of the poor operation efficiency and difficult manufacturing process.
Further, in the lancet 8 shown in FIG. 27, the needle hub 82 and the lancing needle 83 are freely movable relative to the housing 80 after the breakable portion 81 is broken. This allows the lancing needle 83 to project from the housing 80 when the lancet 8 is detached from the lancing apparatus for disposal. Thus, there may be a danger that the lancing needle 83 may stick into a finger, for example.